The present invention relates generally to auditory ossicles prostheses. More particularly, it relates to an auditory ossicles prostheses with a head plate for abutting against an eardrum and a shaft arranged on it for bridging the timpanic cavity from the eardrum up to a stirrup or up to stirrup foot plate, wherein the shaft is provided with a coupling member at its end facing the stirrup.
For the implantation of the auditory ossicles prosthesis, before the implantation it is necessary to determine the length of the prosthesis individually for corresponding patients. Since the required length can be determined first only during the operation, for each operation either a set of prostheses of different lengths or a prosthesis with a variable shaft length are needed. In known, longitudinally adjustable auditory ossicles prostheses, the shaft of the prosthesis is subdivided into a plurality of successive portions, and the successively arranged portions are separated from one another by a cross-sectional reduction at predetermined breaking points. Since with fine auditory ossicles prostheses it is necessary to operate in the region of tenths or hundredths millimeters, the manufacture of the predetermined breakage points is relatively complicated and expensive.
Accordingly, it is an object of present invention to provide an auditory ossicles prosthesis of the above mentioned general type, which is improved so that the separation of the shaft into the individual lengths can be performed with lower manufacturing expenses for the shaft and thereby cost reduction can be obtained.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in an auditory ossicles prostheses in which the head plate has a throughgoing opening for receiving the shaft, and the opening is narrowerable for fixing the shaft. For shortening of the shaft, it is displaced through the opening in the head plate, so that it extends outwardly beyond the outer side of the head plate, so that it can project at the outer side of the head plate and can be cut off there. Subsequently, the opening of the head plate is reduced and thereby the shaft is fixed reliably. Then the adjusted prosthesis can be implanted.
When the auditory ossicles prosthesis is designed in accordance with the present invention, it can be adjusted in a fast and stepless manner to the anatomical characteristics of the patient. For narrowing the opening in the head plate, there are several possibilities.
The periphery of the opening can be interrupted by a slot, and the slot and thereby the opening can be narrowed via a deformable web caulking. Thereby the shaft can be fixed on the head plate fast and with less expense. For the same reason the opening can be provided in the center with a slot, and the opening can be narrowed by compressing the slot. The opening can be located also in the center of two intersecting slots, in which case the opening has a smaller diameter than the shaft diameter.
In order to provide an optimal abutment of the head plate on the ear drum, it can be elliptic or can have rounded edges. Also, it can have at least one passage for controlling the position of the coupling piece by an operator.
In accordance with a further embodiment, the shaft can be provided with a scale. This will facilitate the adjustment of the length of the shaft.
The auditory ossicles prosthesis can be roughened at the side which faces the eardrum and/or stirrup. This provides for an optimal abutment of the auditory ossicles prosthesis against the eardrum or the stirrup.
The components and the whole auditory ossicles prosthesis can be produced by a laser technology. This approach will reduce the manufacturing costs.
The auditory ossicles prosthesis of the invention can be composed of gold and/or titanium. As a result it becomes compatibile with users bodies.
The coupling member of the auditory ossicles prosthesis of the invention can be formed as a bell-shaped structure or as a plunger. Thereby the auditory ossicles prosthesis can be mounted reliably both as a total prosthesis or also as a partial prosthesis on the stirrup. When the bell-shaped coupling member is used, it can be slotted for guaranteeing an optimal hold on the stirrup. The slot can extend parallel to the longitudinal semi-axis of the elliptic head plate. In the bell-shaped structure the slot can have a width preferably of 0.6 mm.
When the prosthesis is formed as a total prosthesis with a plunger-shaped coupling member, it can have a diameter of 0.8 mm and can be provided with a hollow space, to obtain reliable seat on the stirrup foot plate.
For adjusting the shaft length of the auditory ossicles prosthesis of the present invention, a tool is proposed which has two articulately connected legs, with the thickness of the legs changing in a stepped manner over the leg length. At the inner side of the legs depressions are provided for receiving the shaft, and also lateral depressions are provided for receiving the head plate. The shaft of the auditory ossicles prosthesis can be inserted into one of the depressions for receiving the shaft, and in particular at one of the stages of the leg of the tool whose thickness exactly corresponds to the desired length of the shaft. In this way the tool for adjusting the shaft length also has the function of a gauge.
With the special tool and the individually length-adjustable shaft, the shaft length of the auditory ossicles prosthesis during the operation can be adjusted in a shortest time to the exact measurements in the ear of the patient.
The depressions can be formed on the contact-surface to the other leg as semi-circular recesses. Therefore the shaft can be introduced optimally in the depressions at the contact surface to the other leg.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.